This invention relates, in general, to a sand control screen assembly positioned in a production interval of a wellbore and, in particular, to a sand control screen assembly having a seal member that prevents fluid flow from the interior to the exterior of the sand control screen assembly during the treatment of single or multiple formations during a single trip into the well.
It is well known in the subterranean well drilling and completion art that relatively fine particulate materials may be produced during the production of hydrocarbons from a well that traverses an unconsolidated or loosely consolidated formation. Numerous problems may occur as a result of the production of such particulate. For example, the particulate causes abrasive wear to components within the well, such as tubing, pumps and valves. In addition, the particulate may partially or fully clog the well creating the need for an expensive workover. Also, if the particulate matter is produced to the surface, it must be removed from the hydrocarbon fluids using surface processing equipment.
One method for preventing the production of such particulate material is to gravel pack the well adjacent to the unconsolidated or loosely consolidated production interval. In a typical gravel pack completion, a sand control screen is lowered into the wellbore on a work string to a position proximate the desired production interval. A fluid slurry including a liquid carrier and a relatively coarse particulate material, such as sand, gravel or proppants which are typically sized and graded and which are typically referred to herein as gravel, is then pumped down the work string and into the well annulus formed between the sand control screen and the perforated well casing or open hole production zone.
The liquid carrier either flows into the formation or returns to the surface by flowing through a wash pipe or both. In either case, the gravel is deposited around the sand control screen to form the gravel pack, which is highly permeable to the flow of hydrocarbon fluids but blocks the flow of the fine particulate materials carried in the hydrocarbon fluids. As such, gravel packs can successfully prevent the problems associated with the production of these particulate materials from the formation.
It has been found, however, that following a gravel packing operation, the fluid inside the sand control screen tends to leak off into the adjacent formation. This leak off not only results in the loss of the relatively expensive fluid into the formation, but may also result in damage to the gravel pack around the sand control screen and the formation by, for example, fracturing a formation when it is not desirable to fracture that formation. This fluid leak off is particularly problematic in cases where multiple production intervals within a single wellbore require gravel packing as the fluid remains in communication with the various formations for an extended period of time.
In other cases, it may be desirable to perform a formation fracturing and propping operation prior to or simultaneously with the gravel packing operation. Hydraulic fracturing of a hydrocarbon formation is sometimes necessary to increase the permeability of the formation adjacent the wellbore. According to conventional practice, a fracture fluid such as water, oil, oil/water emulsion, gelled water or gelled oil is pumped down the work string with sufficient volume and pressure to open multiple fractures in the production interval. The fracture fluid may carry a suitable propping agent, such as sand, gravel or proppants, which are typically referred to herein as proppants, into the fractures for the purpose of holding the fractures open following the fracturing operation.
The fracture fluid must be forced into the formation at a flow rate great enough to fracture the formation allowing the entrained proppant to enter the fractures and prop the formation structures apart, producing channels which will create highly conductive paths reaching out into the production interval, and thereby increasing the reservoir permeability in the fracture region. As such, the success of the fracture operation is dependent upon the ability to inject large volumes of hydraulic fracture fluid along the entire length of the formation at a high pressure and at a high flow rate.
It has been found, however, that it is difficult to fracture multiple formations traversed by the wellbore that are within a relatively close proximity of one another. This difficulty is the result of the complexity and length of the permanent downhole tools and the associated service tools used to perform the fracture operation. Accordingly, if formations are closer together than the axial length required for the permanent downhole tools and service tool, then certain of the formations cannot be isolated for individual treatment processes.
Therefore, a need has arisen for an apparatus and a treatment method that provide for the treatment of multiple formations that are located relatively close to one another by allowing the use of relatively simple and compact permanent downhole tools and service tools. A need has also arisen for an apparatus and a treatment method that allow for the gravel packing of one or more production intervals while preventing fluid loss into adjacent formations.
The present invention disclosed herein comprises a sand control screen assembly and method for treating multiple formations traversed by a wellbore in a single trip. The sand control screen of the present invention provides for the treatment of relatively closely spaced formations by allowing the use of relatively simple and compact permanent downhole tools and service tools. In addition, the sand control screen of the present invention prevents undesirable fluid loss from the interior thereof to an adjacent formation.
The sand control screen assembly of the present invention includes a base pipe with multiple openings designed to allow fluid flow therethrough. A filter medium is positioned about the exterior of the base pipe to filter particulate matter during hydrocarbon production. A seal member is positioned within the openings of the base pipe to selectively prevent fluid flow through the sand control screen assembly. The seal member may include plugs, a sleeve, one-way valves or the like to achieve this result. If the seal member uses one-way valves, the one-way valves may be positioned within the openings of the base pipe to prevent fluid flow from the interior of the base pipe to the exterior of the base pipe. The one-way valves are actuatable to allow fluid flow from the exterior of the base pipe to the interior of the base pipe to, for example, allow fluid returns to flow therethrough during a gravel packing operation or to allow production fluids to flow therethrough.
A variety of downhole treatment operations may be achieved using the sand control screen assembly of the present invention. For example, one treatment method involves locating a sand control screen assembly within a production interval of a wellbore, preventing fluid flow from the interior to the exterior of the sand control screen assembly with a seal member disposed within the base pipe that controls fluid flow through the openings of the base pipe and pumping a treatment fluid into the production interval. In this method, the treatment fluid may be a fracture fluid or a gravel packing fluid. Alternatively, the treatment fluid may be a series of treatment fluids.
For example, in a first phase of a treatment process, the treatment fluid may have a relatively low density and a relatively low viscosity and contain a relatively high concentration of solid agents therein. These solid agents may be used to form a sand plug within the interior of the sand control screen assembly. In a second phase of the treatment processes, the treatment fluid may have a relatively high density and a relatively high viscosity but contain little or no solid agents. This treatment composition is suitable for formation fracturing. In a third phase of the treatment process, the density and viscosity of treatment fluid may be reduced and the treatment fluid will again contain a relatively high concentration of solid agents therein. These solid agents are used to prop the formation fractures and pack the production interval between the sand control screen assembly and the wellbore.
In the downhole treatment operations of the present invention using the sand control screen assembly of the present invention, fluid flow is prevented from the interior to the exterior of the sand control screen assembly of the present invention. By preventing this fluid flow both during and following certain treatment operations, fluid loss is prevented, damage to the formation and the gravel pack is reduced and simpler, more compact service tools and permanent downhole tools may be utilized. In addition, use of such simpler, more compact service tools and permanent downhole tools makes the treatment operations of the present invention using the sand control screen assembly of the present invention particularly advantageous for treating multiple formations traversed by a wellbore on a single trip.